フェライト型球状黒鉛鋳鉄の低サイクル疲労寿命に及ぼす黒鉛粒数の影響

概要

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This paper deals with the effect of nodule count on the low-cycle fatigue life of ferritic ductile cast iron. Stress amplitude-controlled fatigue tests are conducted on ferritic ductile cast iron with different nodule count, i. e. high nodule count (HNC), and low nodule count (LNC) with same chemical composition and heat treatment. The difference of nodule count yields difference of fatigue mechanism in HNC and LNC. The fatigue life of both materials satisfies the Manson-Coffin relationship and shows an opposite trend depending on the fatigue region. The Fractgraphic observation reveals that the crack initiation site of LNC is originated at spheroidal graphite, while a coarse graphite controls the crack initiation in HNC. The increase of graphite size in LNC results in enhancing the internal notch effect of graphite.
1994-04-25